In order to advance our understanding of self-injury this study (July 2007 to June 2010) investigated the experiences of adults who had used or were using self-injury. This was achieved by obtaining verbal narrative accounts of their experiences of using self-injury from its onset during childhood or early adolescence, throughout adolescence and into adulthood. These verbatim accounts formed a corpus of data which was analysed using a grounded theory method. The analysis established seven robust categories involved in the use of self-injury. By thoroughly examining these categories the substantial theory that self-injury develops as a versatile multi-functional behaviour was generated.